Process for casting concrete pipe



July 1, 1958 e. R. JESSEN ETAL 2,

PROCESS-FOR CASTING CONCRETE PIPE Filed March 5, 1954 2 Sheets-Sheet 1INVENTORS 6501955 2. MES-95V me: (a CH/ZULU/VD BY 01 W5 July 1, 1958 G.R. JESSEN EI'AL PROCESS FOR CASTING CONCRETE PIPE 2 Sheets-Sheet 2INVENTORS 650965 ,e. JESSE/(I 00a m CH4NLU/VD BY fif'fOEA/EVS FiledMarch 3, 1954 PROCESS FOR CASTING CONCRETE PIPE George Ronald Jessen andCarl Wilmer Chanlund, Salt Lake City, Utah, assignors, by mesneassignments, to Cen-Vi-Ro Pipe Corporation, South Gate, Calif., acorporation of Delaware Application March 3, 1954, Serial No. 413,754 6Claims. Cl. 25-155} This invention relates to the production of concretepipe and the like, and has particular reference to a process forcentrifugally casting concrete pipe of the type having bell and spigotjoints.

In the manufacture of concrete pipe two basic types of joints arecommonly used. These are the tongue and groove joint wherein the pipesections are continuously cylindrical, and the so-called bell and spigotjoint wherein cepted that, regardless of; the specific methodofmanufacture, two elements are necessary, namely, a mold having a flaredend, and a so-called forming ring attached to the flared end, the ringhaving an outer surface de signed to mold the inner mating surface ofthe pipe bell section. This mold and ringarrangement has not beenentirely successful when used in centrifugal spinning processesutilizing a conventional Wet concrete mix. ,The primary reason for thisis that the excess water which is removed during thespinning carrieswith it fines from the coricrete,.the flow of water and fines passingbetween the bell forming: ring and the concrete and, inso doing, Washingthe mating surface of the bell. The finished mating surface. thusexhibits flow channels as well as a soft slurry surface. It is readilyapparent thatfor pressure pipes, the accuracy and quality of the bellmating surface must be maintained at an optimum to avoid leakage, and itis further apparent that a washed and/orsoft surface is notsatisfactory. One solution to this problem is to grind the bell sectionsurface after casting of the wet mix, but this procedure is, of course-,economically prohibitive. The most widely accepted solution heretoforehas emailed the use of steel joint. rings embedded in the pipe. Thisarrangement is also subject to inherent disadvantages in that the jointsmust be mortar-protected in an attempt to inhibit corrosion. of thesteel rings, sometimes without complete success. One of theprincipalobjects of this invention is, therefore, to provide a methodfor casting concrete pipe of the bell and spigot joint type, whichmethod is notsubjectto the inherent disadvantages of themethodsheretofore pro posed and used. g

In our copending application; Serial No; 187,452 filed September 29,1950, now Patent 2,671,260 granted March 9, 1954 entitled Method andApparatus for Making Pipe From Concrete and Like Materials, isdiseloseda method and apparatus for casting concrete pipe utilizing asnbstan'tially dry concrete mix, i; e;, a having a' relatively lowcement-water ratio such as, for example; of the order of about 0.25. Ithas been found that, in addition to the advantages of such a mix, asoutlined insaid copending application, a substantially dry concrete mixis highly suitable for use in making concrete pipe of the bell andspigot joint type, due in part to the fact that the run-off of excesswater during the spinning of the mold is insufiicient to cause washingof the bell section mating surface. Another object of this invention isto provide a process for forming concrete pipe of the bell and spigottype utilizing a substantially dry concrete mix.

Yet another object of this invention is to provide a process for theproduction of concrete pipe of the bell and spigot type wherein a seriesof novel steps are utilized in producing the bell section of the pipe.

Other objects and advantages of this invention, it is believed, will bereadily apparent from the following detailed description of a preferredembodiment thereof when read in connection with the accompanyingdrawings.

In the drawings:

Figure 1 is a front elevation of a centrifugal casting apparatus adaptedto be used in carrying out the process of this invention.

Figure 2 is a vertical side sectional elevation of a portion of theapparatus.

Figure 3 is an enlarged fragmentary sectional view illustrating the bellsection of the mold and finished P P Figure 4 is a side elevation,partially in section, illustrating the apparatus utilized in carryingout the process of i this invention.

h Figure S is a fragmentary perspective View illustrating the concretedelivery conveyor.

v Figure 6 is a vertical sectional elevation of the finished Referringnow to the drawings, the centrifugal casting portion of the apparatus isof the type set forth in our said copending application, Serial No.187,452. As shown best in Figures 1 and 2, the apparatus includes aframe 10 and a-mold 11 supported for rotation on two pairs of trunnions14 and 15. The trunnions, preferably of pneumatic construction, aremounted on suitable axles 16 driven through a transmission 18 by meansof a motor 20. A roller compacting element 22 extends longitudinallythrough the mold 11, being rotatably supported on arms 24 at each endthereof. The arms are pivotally connected to the frame by means of ashaft 26 mounted insuitable bearings 27. Means are provided for raisingand lowering the compacting roller and as shown in Figure 1, these meansmay include the power cylinder assemblies 29, the piston rods 30 ofwhich are pivotally connected to the arms 24. Means are also providedfor vibrating the mold at a high frequency and as shown, these means mayinclude the high frequency vibrator element 35 adapted to be moved intocontact with the outer Wall of the mold by means of its supporting arm36 which is pivotally connected at a point intermediate the ends thereofto the shaft 26, the end of the arm remote from the vibrator elementbeing pivotally connected to the piston rod 38 of a power cylinderassembly 40. I

As shown in Figure 4, the apparatus utilized in carrying out the processof this invention additionally comprises a concrete delivery mechanismgenerally indicated 50, including an endless conveyor 51 mounted on acarrier 53, the carrier being provided with flanged wheels 54 formovement on the tracks 55. A concrete mixing apparatus 56 may besuitably mounted on the carrier 53 and provided with a chute 58 forfeeding concrete to the conveyor 51.

The conveyor 51 comprises an endless belt 60 extending between endrollers 62 and driven through a suitable transmission 64 by means of themotor 65. The rollers 62 are mounted in an I-beam member 65 which alsocarries support rollers 70 for the belt.

As shown in the drawings, the mold 11 is generally cylindrical and isprovided at one end with a bell section. or flared, bell-forming portion80 which conforms to the outer surface of the bell section of the pipeto be produced. A bell forming ring 82, preferably of steel, isprovided, the ring having an annular end wall 82a, an intermediatecylindrical portion 82b, and an inner annular wall 820, thus beingsuitably shaped to form the inner and endsurfaces of the pipe bellsection. Means are provided for securing the ring 84 to the mold, and asshown in the drawings, these means include the opposed annular grooves83 and 84 in the ring and mold respectively, and a split snap ring 85extending into both of these grooves. Similarly, a spigot forming ring86 is secured to the spigot end 87 of the mold by means of the splitsnap ring 88 seated in annular grooves in the ring 86 and mold,respectively.

In carrying out the process of this invention, a cagelike steelreinforcing section (not shown) for the pipe in placed in the mold andthe supporting trunnions 14 and are put into operation, causing the mold11 to be rotated at a speed sufiicient only to maintain the concrete inplace as it is poured in the manner described below. This speed is about3040% of the maximum, or spinning speed, the maximum spinning speedbeing in the vicinity of 4500 ft./min., but varying widely dependingupon pipe size. The vibrator element 35 is actuated to vibrate at afrequency of several thousand cycles per minute. With the concretedelivery mechanism 50 in the position shown in Figure 4, and with themold rotating at the speed indicated, the conveyor 51 is then actuatedto deliver the substantially dry concrete mix into the bell section ofthe mold. The mechanism 50 is maintained in the position shown until theconcrete level is substantially above that of the forming ring. Themechanism 50 is then slowly withdrawn with continued delivery ofsubstantially dry concrete, filling the remainder of the mold to formthe barrel of the pipe.

When the mold is filled, the vibrator element is deenergized and theroller compacting element 22 is lowered to bear against the. cylindricalrolling edges 90 and 91 of the forming rings 82 and 84. This rolleraction forces the concrete, which was placed above the forming ring 82,downinto the bell section of the mold. More concrete is then added andforced into the bell section by the roller as needed until the mold willreceive no more, the roller functioning both to compact the concrete bypressure and also as a screed to obtain the desired uniform inside pipediameter.

The speed of the mold is then increased slightly, to 50-60% of themaximum spinning speed, and the vibrator element is again energized,with the roller 22 still in the compacting position, for a shortinterval to assure complete compaction and uniform inside diameter, andto relieve any tension existing in the reinforcing steel. After thissimultaneous vibrating, spinning and compacting step, the roller israised out of contact with the pipe, the vibrator element isde-energized, and the mold is "spun out at the maximum, or spininngspeed to complete the pipe.

The completed pipe 100 is shown in Figure 6, having a generallycylindrical barrel section 101, a bell section 102 and a spigot end 103.

While a specific embodiment of this invention has been shown anddescribed, it is not intended to limit the same to the exact details ofthe construction set forth, and it embraces such changes, modificationsand equivalents of the parts and their formation and. arrangement ascome within the purview of the appended claims.

We claim:

1. In a method of forming, from a substantially dry concrete mix,concrete pipe of the type having a bell end,the steps comprisingspinning a hollow cylindrical mold having a bell-forming portion at onerate, introducing a substantially dry concrete mix into the mold,contacting a portion of the length of the mold progressively throughoutthe circumference during said spinning with a vibrator at a fixedlocation to impart high frequency vibrations to the mold to pack theconcrete mix against the mold while the mold is being filled, applyingpositive pressure to the concrete mix to further pack the same againstthe mold while said mold is spinning and being vibrated, removing saidpositive pressure and said vibrator, and spinning said mold at a morerapid rate to impart additional centrifugal force to said concrete mix.

2. In a method of forming, from a substantially dry concrete mix,concrete pipe of the type having a bell end, the steps comprisingspinning a hollow cylindrical mold having a bell-forming portion at onerate, introducing a substantially dry concrete mix into the mold byfirst introducing said mix into the bell-forming portion during saidspinning to fill the same and then introducing said mix into theremainder of the mold progressively from the bell-forming portion to theend opposite thereto contacting at a location adjacent the bell-formingportion a portion of the length of the mold progressively throughout thecircumference with a vibrator at a. fixed location to impart highfrequency vibrations to the mold to pack the concrete mix against themold while the mold is being filled and rotated, applying positivepressure to the concrete mix to further pack the same against the moldwhile said mold is spinning and being vibrated, removing said positivepressure and said vibrator, and spinning said mold at a more rapid rateto impart additional centrifugal force to said concrete mix.

3. In a method of forming, from a substantially dry concrete mix,concrete pipe of the type having a bell end, the steps comprisingspinning a hollow cylindrical mold having a bell-forming portion at onerate, introducing a substantially dry concrete mix into the mold byfirst introducing said mix into the bell-forming portion to fill thesame and then introducing said mix into the remainder of the mold,contacting progressively throughout the circumference a portion of thelength of the mold with a vibrator at a fixed location to impart highfrequency vibrations to the mold to pack the concrete mix against themold while the mold is being filled, removing said vibrator, applyingpositive pressure to the concrete mix to further pack the same againstthe mold While said mold is spinning, again imparting high frequencyvibrations to said mold progressively throughout the circumference whilesaid mold is spinning and receiving the application of pressure,removing said positive pressure and said vibrator, and rapidly spinpingsaid mold to impart additional centrifugal force to said concrete mix.

4. In a method of forming, from a substantially dry concrete mix,concrete pipe of the type having a bell end, the steps comprisingspinning a hollow cylindrical mold having a flared, bell-forming endportion, introducing a substantially dry concrete mix into the mold byfirst introducing said mix into the bell-forming portion to fill thesame to overflowing and then introducing said mix into the remainder ofthe mold progressively throughout the length and in quantity adapted tooverfill the mold, applying positive pressure to the concrete mix topack the same against the mold while said mold is spinning, removingsaid pressure, and increasing the speed of spinning of the mold toimpart additional centrifugal force to said concrete mix.

5. In a method of forming, from a substantially dry concrete mix,concrete pipe of the type having a bell end, the steps comprisingspinning at a selected rate a hollow cylindrical mold having a flared,bell-forming end portion, introducing a substantially dry concrete mixinto the mold by first introducing said mix into the bellforming portionto fill the same and then introducing said mix into the remainder of themold, applying to the mold progressively throughout the circumferencehigh frequency vibrations throughout a given portion along the length ofthe mold to pack the concrete mix against the mold while the mold isbeing filled, removing said vibrations, applying positive pressure tothe concrete mix to further pack the same against the mold While saidmold is spinning, increasing the speed of spinning of the mold, againimparting high frequency vibrations to said mold progressively aroundthe entire circumference While said mold is spinning and receivingtheapplication of pres sure, removing said pressure and vibrations, andfurther increasing the speed of spinning of the mold to impartadditional centrifugal force to said concrete mix.

6. In a method of forming, from a concrete mix, concrete pipe of thetype having a bell end, the steps comprising spinning a hollowcylindrical mold having a flared, bell-forming end portion at a selectedrate of about 30 40% of the maximum spinning rate, introducing aconcrete mix into the mold by first introducing said mix into thebell-forming portion to fill the same and then introducing said mix intothe remainder of the mold, applying high frequency vibrations to themold at several thousand cycles per minute at a progressive locationabout the circumference and along a portion of the length of the mold sothat the vibrations are progressively applied around the entirecircumference of the mold to pack the concrete mix against the moldwhile the mold is being filled, removing said vibrations, applyingpositive pressure to the concrete mix to further pack the same againstthe mold While said mold is spinning, increasing the speed of spinningof the mold to a rate equal to about 60% of the maximum spinning rate,again imparting high frequency vibrations of several thousand cycles persecond to said mold While said mold is spinning and receiving theapplication of pressure, re moving said pressure and vibrations, andfurther increasing the speed of spinning of the mold to full spinningspeed of approximately 4500 feet per minute to impart additionalcentrifugal force to said concrete mix.

References Cited in the file of this patent UNITED STATES PATENTS1,576,127 Austin Mar. 9, 1926 1,807,053 Vicenzi May 26, 1931 1,895,740Ukropina Jan. 31, 1933 1,954,904 Walter Apr. 17, 1934 2,008,074 IsmanJuly 16, 1935 2,109,421 Halkyard Feb. 22, 1938 2,166,175 Porter July 18,1939 2,296,018 Boyle Sept. 15, 1942 2,614,312 Rankin et al Oct. 21, 19522,671,260 lessen et al Mar. 9, 1954

